JPS645808B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to an electric injection device for an injection molding machine.

(b) Conventional technology There are two types of injection devices for conventional injection molding machines: fully hydraulic type and hydraulic/electric type. A fully hydraulic injection device uses a hydraulic motor to rotate the screw for plasticizing the resin material, and a hydraulic cylinder to move the screw for injecting the molten resin. It is.
In addition, a hydraulic/electric injection device uses an electric motor to rotate the screw for plasticizing, and moves the screw for injection using hydraulic pressure.

(c) Problems to be solved by the invention The injection device of the conventional injection molding machine as described above is
In any case, a hydraulic cylinder is used, and the gaskets and sealing members used to seal the high-pressure oil tend to wear out, requiring periodic replacement, and operation may be halted due to oil leaks. The problem was that there are many factors that reduce productivity. Furthermore, since hydraulic equipment is used, there is a limit to the stability of the dimensions, weight, etc. of the molded product due to changes in oil temperature, outside temperature, etc. The present invention solves the above-mentioned problems and provides an electric injection molding machine for injection molding machines that eliminates the need for periodic replacement of gaskets, etc., eliminates oil leakage accidents, and allows stable molding. The purpose is to obtain equipment.

(d) Means for solving the problems The present invention achieves the above object by electrifying both plasticization and injection and controlling the plasticization stroke based on the rotation of the electric motor. That is, the electric injection device for an injection molding machine according to the present invention includes: a first electric motor capable of driving a screw in an injection molding machine cylinder in the axial direction via a ball screw mechanism; a second electric motor capable of rotationally driving the screw; A first rotation detector that detects the rotation of the first electric motor, a second rotation detector that detects the rotation of the second electric motor, and a control device that controls the operation of the first electric motor and the second electric motor. The control device rotates the first motor and stops the second motor at the time of injection, and sets the first motor to a free rotation state or a state that generates a small driving force in the forward direction of the screw at the time of starting plasticization. When the two electric motors are rotated and the difference between the cumulative number of revolutions detected by the second rotation detector since the start of plasticization and the cumulative number of revolutions detected since the start of plasticization by the first rotation detector reaches a predetermined value, the second motor is rotated. It has a function of stopping the first electric motor and the second electric motor to finish plasticizing.

(E) Effect With the above configuration, when the first electric motor is rotated and the second electric motor is stopped, the screw moves forward by the ball screw mechanism and injection can be performed. . Also, the first
When the electric motor is brought into a free rotation state and the second electric motor is rotated, the screw is driven to rotate, the resin material is plasticized within the cylinder, and the screw is retracted by the resin pressure. The plasticizing stroke of the screw is proportional to the difference between the cumulative rotation speed of the second electric motor and the cumulative rotation speed of the first electric motor, so when this difference reaches a predetermined value, both electric motors are stopped. , the screw can be stopped at the metering stop position. Note that during the plasticizing stroke, the first
By generating a relatively small driving force in the forward direction of the screw in the electric motor, it is possible to provide an appropriate resistance force (that is, a force equivalent to the back pressure of the screw in a hydraulic system) against the backward movement of the screw.

(F) Embodiments Hereinafter, embodiments of the present invention will be described with reference to Nos. 1 and 2 of the attached drawings.
This will be explained based on the diagram.

A screw 12 is inserted into a cylinder 10 of an injection molding machine. A casing 14 is attached to the rear end side of the cylinder 10 (upstream side in the resin flow direction). The casing 14 includes a housing 16 and a cover 18, which define a chamber 20. A rotatable and axially movable intermediate shaft 22 is provided within this chamber 20 . The intermediate shaft 22 has a small diameter shaft portion 24 and a large diameter shaft portion 26 . The tip of the small diameter shaft portion 24 is connected to the screw 12 by a spline. The small diameter shaft portion 24 is rotatably and axially movably supported by sliding bearings 36 and 38 attached to the housing 16. intermediate shaft 22
A nut member 54 having a female thread that constitutes a ball screw mechanism 52 together with a male thread 50 provided on the shaft 48 is fixed to the large diameter shaft portion 26 side. A shaft 48 provided with a male thread 50 is rotatably supported with respect to the cover 18 by a thrust bearing 56 and a bearing 58. The shaft 48 is connected to a first electric motor 70 outside the casing 14 . The first electric motor 70 includes a first pulse generator 72
(first rotation detector) is provided. The end of the shaft 48 inside the housing 14 is supported against the inner diameter of the intermediate shaft 22 by a linear motion bearing 75.
The dimension between the inner diameter bottom of the intermediate shaft 22 and the tip of the shaft 48 when the intermediate shaft 22 is moved to the leftmost position in FIG. 1 is L as shown. That is,
The intermediate shaft 22 can be moved in the axial direction by the maximum L dimension. A driven gear 82 is attached to the outer periphery of the large diameter shaft portion 26 of the intermediate shaft 22 by a key 81 so as to rotate together with the intermediate shaft 22 . The driven gear 82 meshes with a drive gear 83 with a collar 83a, which is connected to the shaft 84 by a sliding key 85. The sliding key 85 has a length equal to or larger than the L dimension. The shaft 84 is rotatably supported by bearings 86 and 87 relative to the housing 16 and cover 18. A portion of the shaft 84 that protrudes to the outside of the casing 14 is connected to the second electric motor 71 . The second electric motor 71 is provided with a second pulse generator 73 (second rotation detector). The aforementioned first pulse generator 72
The signals from the second pulse generator 73 are input to the control device 100. Further, the operation of the first electric motor 70 and the second electric motor 71 is controlled by electric power from the control device 100.

Next, the operation of this embodiment will be explained. 1st
The figure shows the injection completed state. When the injection is completed, the first electric motor 70 is brought into a free rotation state by the control device 100, and the second electric motor 71 is caused to start rotating. When the shaft 84 is rotated by the second electric motor 71, the intermediate shaft 22 is rotated via the drive gear 83 and the driven gear 82. intermediate shaft 22
When the screw 12 rotates, the screw 12 connected to the screw through a spline rotates within the cylinder 10, melting and plasticizing the resin material supplied from the material supply port 10a to the inner diameter of the cylinder 10. (left side in Figure 1). As the molten resin transferred to the front of the cylinder 10 increases, the screw 12 rotates and retreats (moves to the right in FIG. 1). Therefore, the intermediate shaft 22 similarly moves to the right in FIG. Since the shaft 48 is connected to the intermediate shaft 22 by a ball screw mechanism 52, it rotates at a certain rotational speed as the intermediate shaft 22 rotates, but it rotates at a rotational speed higher than the rotational speed of the intermediate shaft 22. Never. Therefore, the nut member 54 rotates relative to the external thread 50 and moves to the right in FIG. In addition,
As the intermediate shaft 22 moves, the driving gear 83 moves along the sliding key 85 to follow the intermediate shaft 22 while being engaged with the driven gear 82 due to the action of the collar 83a. When the intermediate shaft 22 and the screw 12 move by the stroke S in this way, the control device 100 stops the rotation of the first electric motor 70 and the second electric motor 71, completing the plasticizing stroke. This control is performed by That is, as shown in FIG.
00 indicates that the pulse signals from the first pulse generator 72 and the second pulse generator 73 are respectively output to the counter 10.
2 and 104, and the difference in the cumulative number of pulses obtained by the counters 102 and 104, respectively, is calculated by the calculator 106, and then the comparator 108
The difference in the cumulative number of pulses is compared with a predetermined set value, and when the difference in the cumulative number of pulses reaches the set value, a signal indicating that the stroke is completed is output from the comparator 108 to the drive circuits 110 and 112. is,
Drive circuits 110 and 112 stop the first electric motor 70 and the second electric motor 71, respectively, based on this signal. Difference in the cumulative number of pulses between the first electric motor 70 and the second electric motor 71 (i.e., difference in cumulative rotation speed)
It is clear from the following description that corresponds to the amount of movement of the intermediate shaft 22 in the axial direction. That is,
When the male screw 50 and the nut member 54 that constitute the ball screw mechanism 52 rotate at the same rotational speed, the nut member 54 (that is, the intermediate shaft 22) does not move in the axial direction, and the male screw 50 and the nut member 54 rotate at the same rotational speed. When there is relative rotation between the nut member 54 and the nut member 54, the nut member 54 moves in the axial direction. The amount of movement of the nut member 54 is proportional to the amount of relative rotation with the male screw 50 (ie, the cumulative relative rotation number). The male screw 50 rotates in unique correspondence with the first electric motor 70, and the nut member 54 also rotates in unique correspondence with the second electric motor 71 via the drive gear 83 and the driven gear 82. Therefore, the amount of relative rotation between the male screw 50 and the nut member 54 corresponds to the difference between the cumulative number of rotations of the first electric motor 70 and the cumulative number of rotations of the second electric motor 71. For this reason, the first
The difference between the cumulative number of pulses of the pulse generator 72 and the cumulative number of pulses of the second pulse generator 73 is proportional to the amount of movement of the intermediate shaft 22. Note that the control device 100
is provided with a stroke setting device 114,
This allows the set value of the comparator 108 to be changed as necessary. By changing this set value, the amount of movement of the intermediate shaft 22 (that is, the amount of molten resin to be plasticized) can be set. Furthermore, by displaying the stroke position on the stroke position display 116 based on the difference in the cumulative number of pulses, it becomes possible to observe the stroke state of the screw 12.

When the first electric motor 70 and the second electric motor 71 are stopped as described above and the plasticizing stroke is completed, the injection stroke is performed next. That is, the first electric motor 70 is rotated while the second electric motor 71 is stopped. The intermediate shaft 22 and the nut member 54 integrated therewith are connected to a driven gear 82 and a driving gear 8.
3 and the second electric motor 71 via the shaft 84, it cannot rotate. Therefore, when the male thread 50 of the shaft 48 is rotated by the first electric motor 70, the nut member 54 moves to the left in FIG. 1 due to the action of the ball screw mechanism 52. Therefore, the nut member 54, the intermediate shaft 22, and the screw 12 connected thereto move to the left in FIG. As a result, the plasticized and melted resin within the cylinder 10 is injected. Note that in this case as well, the driving gear 83 moves together with the driven gear 82 to follow the intermediate shaft 22. In this way, the state shown in FIG. 1 is reached again, and the injection stroke is completed.
One cycle is completed with the above steps, and the same operation is repeated thereafter. As a result, the driving force of the first electric motor 70 moves the screw 12 for injection, and the second electric motor 71, which rotationally drives the shaft 84, rotates the screw 12 for plasticization. .
That is, both the injection operation and the plasticizing operation are motorized and do not require hydraulic drive. Further, since the stroke of the screw 12 can be electrically detected as the difference in the cumulative rotational speed of the second electric motor 71 and the first electric motor 70 from the start of the stroke, remote control of the plasticizing stroke becomes easy.

In addition, in the above description, the first electric motor 7 is
0 is a free rotation state, but it is also possible to supply a relatively small amount of electric power to the first electric motor 70 during plasticization to generate a plasticization back pressure to enable stable plasticization. That is, during plasticization, the first electric motor 70 is operated to generate a relatively small driving force in the direction of advancing the nut member 54 via the ball screw mechanism 52. When the driving force of the first electric motor 70 is generated in this manner, this force acts as resistance against the retreat of the intermediate shaft 22, and acts in the same manner as plasticizing back pressure, thereby making it possible to perform stable plasticizing.

(G) Effects of the Invention As explained above, according to the present invention, both the rotation of the screw for plasticizing and the stroke of the screw for injection are motorized, and the stroke of the screw is equal to the cumulative rotational speed of the two electric motors. Since the control is based on the difference between
It is also possible to apply a force similar to the plasticizing back pressure using an electric motor.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an electric injection device of an injection molding machine according to the present invention, and FIG. 2 is a diagram showing a control device of the electric injection device of the injection molding machine shown in FIG. 10... cylinder, 12... screw, 22...
... Intermediate shaft, 50 ... Male thread, 52 ... Ball screw mechanism, 54 ... Nut member, 70 ... First electric motor, 71 ... Second electric motor, 72 ... First pulse generator (first rotation detection 73... second pulse generator (second rotation detector), 100... control device.

Claims (1)

[Claims] 1. A first electric motor capable of driving the screw in the injection molding machine cylinder in the axial direction via a ball screw mechanism, a second electric motor capable of rotationally driving the screw, and a first rotation detector that detects the rotation of the first electric motor. and a second rotation detector that detects the rotation of the second electric motor, and a control device that controls the operation of the first electric motor and the second electric motor, and the control device rotates the first electric motor during injection. At the same time, the second motor is stopped, and when plasticization starts, the first motor is set to a free rotation state or a state that generates a small driving force in the screw advance direction, and the second motor is rotated. An injection molding machine configured to stop a first electric motor and a second electric motor to terminate plasticization when a difference in cumulative rotation speed detected by one rotation detector from the start of plasticization reaches a predetermined value. Electric injection device.